My three favorite roleplaying games to play (I have several other favorites to read) are Dungeons & Dragons (and its various descendants), Star Wars Saga Edition (which I suppose is also a descendant of D&D), and Call of Cthulhu. The first orbits a vast body of fantasy fiction around the twin axes of J.R.R. Tolkien and R.E. Howard. The second obviously expands (enormously) on the space fantasy films. The third is based on a body of fiction surrounding H.P. Lovecraft’s Mythos.
Few popular RPGs aren’t based on a genre defined by an author or a group of authors who define a subgenre. The World of Darkness owes a great deal to Anne Rice, who of course owes a similar debt to every Gothic novel ever. Shadowrun and Cyberpunk wouldn’t exist without William Gibson and his comrades in the movement. And every Pulp adventure game really should open with a dedication to Lester Dent and the other gods of his pantheon.
What are your favorite games clearly based on a single author or film or TV show? What games have you played that clearly owe no debt to a literary or film or TV source?